1. Field of the Invention
The present invention relates to a method for manufacturing a liquid discharge head substrate.
2. Description of the Related Art
An ink jet recording head that has been adapted and used as a well known liquid discharge head has an arrangement much like that illustrated in FIG. 3. As shown in FIG. 3, a through hole is opened from the reverse to the obverse face of a silicon substrate 101 where heaters 102 are mounted on the obverse face, and serves as an ink supply port 113, via which ink is supplied from the reverse to the obverse side of the silicon substrate 101.
A method for manufacturing such an ink jet recording head is disclosed in U.S. Pat. No. 6,143,190. The use of this manufacturing method is proposed to prevent discrepancies in the opening diameter of an ink supply port 113, a through hole, and includes the following processes: 1) a process for forming on the obverse face of a silicon substrate, at a location whereat an ink supply port is to be formed, a sacrificial layer through which selective etching of substrate material may be performed; 2) a process for forming a passivation layer having a moderate etching resistance, on the silicon substrate, to cover the sacrificial layer; 3) a process for forming an etching mask layer, on the reverse face of the silicon substrate, in which an opening corresponding to the sacrificial layer is formed; 4) a process for performing crystal anisotropic etching of the silicon substrate until the sacrificial layer at the opening is exposed; 5) a process for removing the sacrificial layer by etching the portion whereat the sacrificial layer is exposed as a result of the anisotropic etching of the silicon substrate; and 6) a process for removing part of the passivation layer and forming an ink supply port.
Another manufacturing method is disclosed in U.S. Pat. No. 6,805,432. According to this method, dry etching is performed using a mask mounted on the reverse of a silicon substrate, and then, crystal anisotropic etching is performed using the same mask. Thus, an ink jet recording head can be obtained.
Recently, requests for a downsized ink jet recording head have greatly increased, especially is this so for a color ink jet head for which multiple ink supply ports are formed in a single substrate.
However, since the method disclosed in U.S. Pat. No. 6,143,190 employs anisotropic wet etching for the formation of an ink supply port, a long etching period is required. In addition, according to this method, since the opening size is determined in accordance with the {111} plane along the silicon crystal axis, the opening size of the ink supply port on the reverse of the silicon substrate is increased, and downsizing of the head is therefore difficult. According to the method disclosed in U.S. Pat. No. 6,805,432, since one mask is employed for both dry etching and wet etching, the opening width of the ink supply port on the reverse of the silicon substrate is determined in accordance with the width of the mask on the reverse side of the silicon substrate and the amount of material removed by dry etching. Therefore, when the width of the ink supply port is to be narrowed for downsizing, a small opening must be formed in the mask, the anisotropic wet etching period must be shortened and the amount of material removed by side etching in the opening face must be reduced. To do this, the amount of material removed by dry etching must be increased; however, since an extended period is required for dry etching, in such a case, deterioration of the production efficiency may occur.